The mystery of the Corpse Flower

Friday, January 26, 2007
Daniel Nickrent

CARBONDALE, Ill. -- At one yard in diameter and red as a new Ford Mustang, the Rafflesia plant makes quite a first impression. It stands out amid the jungles full of dull, green vines where it lives.

But the world's largest flower packs a wallop to another sensory organ. It emits an odor similar to decaying meat, helping it attract flies and other insects.

Recently a local professor's research has helped scientists understand more about this flower found only in Southeast Asian countries like Malaysia and Borneo.

Rafflesia, nicknamed the Corpse Flower, has fascinated generations of travelers. The first Westerner to come across it, Englishman Joseph Arnold, feared he was hallucinating.

"Had I been alone and had there been no witnesses, I should have been fearful of mentioning the dimensions of this flower so far does it exceed the dimensions of any flower I've ever seen or heard of," he wrote in 1818.

Today, nearly 200 years after its discovery, Dr. Daniel Nickrent of Southern Illinois University at Carbondale sympathizes with Arnold.

"Basically this guy's freaking out and he doesn't want to tell anyone because they may think he's ingested some sort of tropical plant," Nickrent said, laughing.

Scientists, including Daniel Nickrent of Southern Illinois University, have used genetic analysis to discover the lineage of the Rafflesia, shown above, known for its blood-red bloom a yard wide and its stench of rotting flesh. (Jeremy Holden ~ Submitted photo)

But just as Arnold was shocked, Nickrent has been fascinated by the flower, which attaches to one specific type of jungle vine and gains all its nourishment from that host.

He fell into the world of parasitic plant studies by accident. In 1978, during his graduate work at Old Dominion University, he switched from a focus on ferns to concentrate on the parasitic witch weed because the research was funded by the U.S. Department of Agriculture.

He's never looked back. Today his Web site, www.parasiticplants.siu.edu, is the Net authority on the subject. Nickrent has even written a poem about Rafflesia including the lines, "the tallest tales a botanist tells/Are usually meant to tease ya/But hang on to your hats my friends/This one's about Rafflesia."

Nickrent cultivates his image as the "parasite guy" and even dressed up as Rafflesia for Halloween one year. He says the red giant is the most "charismatic" of the plants he studies but not the only one.

"It's the one that gets the most media attention," he said adding he uses the term "charismatic megaflora" to describe it.

In December, Nickrent and a team of researchers published a discovery about the charismatic Rafflesia in Science magazine. Through DNA analyses of the mitochondria and nuclei of the Rafflesia, his team believe they have placed the parasitic plant on the proper branch of its family tree.

The surprising part is that this family, Euphorbiaceae, is known for having small flowers.

"Nobody guessed it would end up there," Nickrent said.

Other plants in the Euphorbiaceae family include the poinsettia, the cassava shrub and the Irish bell. None has flowers approaching the gigantic size of Rafflesia, which can weigh up to 15 pounds.

During the research, the plant's odd nature made it difficult to place Rafflesia's relationship to other plants. "It just has a lot of unusual things that keep us from classifying it," he said.

'The real boon'

The advent of DNA sequencing, Nickrent's specialty, allowed scientists to look at the plant from a historical angle.

"That's the real boon in all of this. Now we're able to have a look at it from an evolutionary point of view," he said.

As recently as 2004, scientists knew Rafflesia was in the Malpighiales group, which includes more than 10,000 species of plants. But that wasn't nearly specific enough.

"It was like OK, now you've landed on the moon, but which crater are you on?" he said.

After analyzing a great deal of DNA data from this group, Nickrent and his co-authors from Harvard, the University of Wisconsin and the Smithsonian Institution were finally able to locate that crater, the Euphorbiaceae family.

For Nickrent, that discovery makes it all worthwhile.

"It's the idea of discovery, being the first humans ever to see or know something new. There's joy in that," he said.

Now the speculation can begin on how this megaflower evolved.

Part of the explanation for its evolution may be in its life as a parasite. Because it feeds off another plant, Rafflesia has no leaves, no roots and no stems.

"When a plant doesn't have to do photosynthesis or collect water, it can put all of its energy into reproduction," Nickrent said.

Nickrent believes over the years, Rafflesia may have evolved into a larger and larger flower to aid the reproduction process. His studies indicate its flower size has grown 73-fold over the past 46 million years.

"One of the reasons we think the flowers were bigger and bigger is to broadcast smell, to get the pollen-moving insects to see them or smell them. You see it's this big flesh-colored thing with these white marks, and a little fuzz. It looks like a decaying animal," said Nickrent.

Like most plants, Rafflesia comes in both male and female versions. Once the fly collects pollen from the male plant and travels to the female ovary the seed is fertilized.

But Rafflesia makes matters tough on itself. When the flower opens it needs immediate pollination or it begins to die.

"After one day these things start to turn to black slime. Just within a day if it's not pollinated. So sex has to happen soon," Nickrent said.

Then with this new discovery, Nickrent says much more is to be learned about this mysterious plant.

"We don't even know what a seedling looks like. They've never really looked at seedlings attaching to the host in nature," he said.

tgreaney@semissourian.com

335-6611, extension 245

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